Wind turbines have already been manufactured for some time in such quantities that it is quite acceptable to talk about series production. In the end, however, each wind turbine is definitely unique, because deviations from optimum settings also occur in series production. As is known, this is definitely not a phenomenon of series production of just wind turbines. Instead, in many areas of daily life there are default values and an acceptable tolerance range, within which deviations from the predetermined values are acceptable and not problematic.
Because the rotor blades of wind turbines are produced with an extraordinarily high percentage of manual labor and reach considerable dimensions, each individual rotor blade is unique. Thus, a wind turbine with three rotor blades already has three unique blades on its rotor. Therefore, a rotor of one wind turbine is not like any other and even the exchange of one rotor blade changes the entire rotor, within the tolerance range.
Accordingly, the operating behavior of each wind turbine also differs from that of all other wind turbines; even when these are of the same type. Even if the deviations lie within the permissible tolerance range, they can nevertheless still lead to power losses.
Wind turbines and especially their parts mounted outside in the area of the gondola, such as the rotor, but also the anemometer, are subject to the risk of icing, especially in winter. Icing of the anemometer can easily lead to measurement errors, which in turn result in unsuitable control of the wind turbine.
Icing of the rotor involves the risk that persons and things in the area of the wind turbine could be injured or damaged due to falling ice. When rotor blades are covered with ice, it cannot be predicted when or how much ice will fall, and the wind turbine must be stopped, in particular, due to icing of the rotor blades, in order to prevent endangering the area.
In the state of the art, various approaches have become known to prevent this problem. Thus, e.g., heated anemometers are available. The heaters of these anemometers should prevent icing. However, such a heater is not complete protection against icing of the anemometer, because, on one hand, the heater could fail and, on the other hand, even a functional heater cannot prevent the formation of ice to arbitrarily low temperatures.
Various designs have also become known for the rotor blades. For example, rotor blades can be heated in order to prevent any formation of ice. However, for large wind turbines with correspondingly large rotor blades, the power consumption needed is considerable. From DE 195 28 862 A1, a system is known in which the turbine is stopped after there is icing and then the rotor blades are heated in order to eliminate the icing of the rotor blades, with power use optimized as much as possible. However, the detection of icing in the state of the art is frequently realized through the detection of an unbalanced rotor, which results when the rotor drops a part of the already-formed ice.
However, the first time ice falls already represents a danger to the area; with increasing size of the rotor blades their mass also increases, so the fall of relatively small amounts of ice does not lead to a detectable imbalance, and reliable detection of ice formation is difficult.